Three-terminal germanium-on-silicon avalanche photodiode with extended p-charge layer for dark current reduction

Xiaobin Liu; Xuetong Li; Yuxuan Li; Yingzhi Li; Zihao Zhi; Min Tao; Baisong Chen; Lanxuan Zhang; Pengfei Guo; Guoqiang Lo; Xueyan Li; Fengli Gao; Bonan Kang; Junfeng Song

doi:10.1364/PRJ.452004

Journals >Photonics Research >Volume 10 >Issue 8 >Page 1956 > Article

Photonics Research
Vol. 10, Issue 8, 1956 (2022)

Three-terminal germanium-on-silicon avalanche photodiode with extended p-charge layer for dark current reduction

Xiaobin Liu¹, Xuetong Li¹, Yuxuan Li¹, Yingzhi Li¹, Zihao Zhi¹, Min Tao¹, Baisong Chen¹, Lanxuan Zhang¹, Pengfei Guo², Guoqiang Lo², Xueyan Li¹, Fengli Gao¹, Bonan Kang¹, and Junfeng Song^1、3、*

Author Affiliations

¹State Key Laboratory of Integrated Optoelectronics, College of Electronic Science and Engineering, Jilin University, Changchun 130012, China

²Advance Micro Foundry Pte Ltd, Singapore 117685, Singapore

³Peng Cheng Laboratory, Shenzhen 518000, China

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DOI: 10.1364/PRJ.452004 Cite this Article Set citation alerts

Xiaobin Liu, Xuetong Li, Yuxuan Li, Yingzhi Li, Zihao Zhi, Min Tao, Baisong Chen, Lanxuan Zhang, Pengfei Guo, Guoqiang Lo, Xueyan Li, Fengli Gao, Bonan Kang, Junfeng Song. Three-terminal germanium-on-silicon avalanche photodiode with extended p-charge layer for dark current reduction[J]. Photonics Research, 2022, 10(8): 1956 Copy Citation Text

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(a) Structural diagram of three-terminal Ge-on-Si APD. (b) SEM image of pixel units. (c) Electric field simulation diagram of Ge region. (d) Simulated electric field in Si APD area [electric field at different positions of line A in (b)].

Fig. 1. (a) Structural diagram of three-terminal Ge-on-Si APD. (b) SEM image of pixel units. (c) Electric field simulation diagram of Ge region. (d) Simulated electric field in Si APD area [electric field at different positions of line A in (b)].

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(a) Current characteristic diagram at 1550 nm under different input optical power. (b) Responsivity characteristic diagram at 1550 nm under different input optical power. (c) Current characteristic diagram at 1310 nm under different input optical power. (d) Responsivity characteristic diagram at 1310 nm under different input optical power. The figure shows the voltage applied to two terminals Ge and n++ Si.

Fig. 2. (a) Current characteristic diagram at 1550 nm under different input optical power. (b) Responsivity characteristic diagram at 1550 nm under different input optical power. (c) Current characteristic diagram at 1310 nm under different input optical power. (d) Responsivity characteristic diagram at 1310 nm under different input optical power. The figure shows the voltage applied to two terminals Ge and n++ Si.

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Fig. 3. It represents the simulated dark current diagram (current output at the n++ terminal) when different fixed voltages are applied to Ge when the n++ Si voltage is 60 V and p++ Si is grounded.

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Fig. 4. When the n++ Si terminal scanning voltage is 60 V, the p++ Si terminal is grounding, and different fixed voltages are applied to Ge: (a) dark current; (b) current characteristic diagram at 1550 nm under input optical power −20 dBm. (c) Under the fixed Si voltage, the dark current of n++ Si terminal varies with the applied voltage of Ge. (d) Under the fixed Si voltage, the current at 1550 nm at an input optical power of −20 dBm varies with the applied voltage of Ge.

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Fig. 5. (a) Schematic diagram of three-terminal APD. (b) Y direction electric field simulation in Si region [position from B to B′ in (a)]. (c) X direction electric field simulation of Si charge region [position from A to A′ in (a)]. (d) Electric field simulation diagram of Ge region.

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Fig. 6. (a) Photocurrent diagram at 10−7 A. (b) Responsivity at 10−7 A. (c) Photocurrent diagram at 10−8 A. (d) Responsivity at 10−8 A.

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Fig. 7. When the voltage on Ge is −27.5 V. (a) Current characteristic diagram at 1310 nm under different input optical power. (b) Responsivity characteristic diagram at 1310 nm under different input optical power. (c) Current characteristic diagram at 1550 nm under different input optical power. (d) Responsivity characteristic diagram at 1550 nm under different input optical power.

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Fig. 8. When the voltage on Ge is −27.5 V. (a) Avalanche gain at 1310 nm wavelength. (b) Avalanche gain at 1550 nm wavelength.

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Fig. 9. When the applied voltage on p++ Ge is −27.5 V and the input optical power is −20 dBm. (a) Responsivity in O-band. (b) Responsivity in C-band (1530–1560 nm) and L-band (1570–1600 nm).

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Fig. 10. (a) Current at −20 V on Ge. (b) Current at −25 V on Ge. (c) Current at −30 V on Ge. (d) At different voltages on Ge, the photocurrent is greater than the multiple of dark current.

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Fig. 11. (a) The APD has a normalized RF response characteristic at a voltage of Ge at −27.5 V and different Si input voltages. (b) The APD voltage on the Ge is −27.5 V, and the S22 parameters are measured under different Si input voltages. (c) The APD has a normalized RF response characteristic at a voltage of Si at 15 V and different Ge input voltages. (d) The APD voltage on the Si is 15 V, and the S22 parameters are measured under different Ge input voltages [the specific voltage values are shown in (c)].

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Fig. 12. (a) When the voltage is −27.5 V on Ge, the three-terminal APD equivalent circuit model. (b) When the signal ends are input to 15 V, the reflection coefficient is measured and fitted. (c) The relative error values between simulation and practice in (b).

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	$- 10 dBm$	$- 20 dBm$	$- 30 dBm$	$- 40 dBm$
$R_{1}$ at 1310 nm	0.80 A/W	3.16 A/W	6.17 A/W	10.50 A/W
$R_{2}$ at 1310 nm	0.63 A/W	1.80 A/W	1.82 A/W	1.74 A/W
$R_{1}$ at 1550 nm	0.83 A/W	3.55 A/W	6.96 A/W	9.97 A/W
$R_{2}$ at 1550 nm	0.68 A/W	2.36 A/W	2.48 A/W	2.07 A/W

Table 1. Response of Ge to −27.5 V at Different Input Power

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Parameters	$L_{p}$ (nH)	$R_{s}$ (kΩ)	$C_{d}$ (fF)	$R_{d}$ (kΩ)
Values	1375	1.21	45	2.41
Parameters	$C_{c}$ (pF)	$L_{m}$ (μH)	$R_{m} (k Ω)$	$C_{m}$ (pF)
Values	2.8	19.8	0.825	4.2
Parameters	$L_{a}$ (μH)	$R_{a}$ (kΩ)	$C_{a}$ (fF)
Values	196	1	172

Table 2. Fitted Electric Circuit Parameters of a Three-Terminal Avalanche Photodiode under a Reverse Bias of 15 V

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Reference	$λ$ (nm)	Dark Current (A)	Responsivity (A/W)
[34]	1310	$8.4 \times 10^{- 7}$	6.54
[10]	1310	$10^{- 5}$	12.00
[35]	1550	$10^{- 4}$	12.70
[36]	1310	$10^{- 6}$	4.40
[33]	1310	$\sim 10^{- 6}$	5.88
This work	1310	$10^{- 7}$	10.50
This work	1550	$10^{- 7}$	9.97